From Boeings Jet Transport Performance Methods: Chapter 22
EASA regulations
The European Aviation Safety Agency, in its Certification Specifications for Large Aeroplanes CS-25, Book 1 Subpart B, contains precisely the same climb requirements as the FAR25 requirements quoted above. CS 25.121 corresponds to FAR Part 25 Section 25.121.quoted above. Thus the requirements to both FAA and EASA/JAA operators are identical.
wind corrections to required gradients
We said earlier that the gradient requirements quoted above are unrelated to the requirements for obstacle clearance; instead, they’re a means of mandating a minimum acceptable level of surplus energy during a takeoff. Because of this fact, the gradients specified are zero-wind gradients – they are not corrected for the wind expected during the takeoff. The airplane’s surplus energy state is not a function of the wind encountered during the takeoff.
Obviously, however, when we’re concerned with obstacle clearance we must consider the wind since the wind affects the airplane’s path over the ground and hence its ability to clear any obstacles.